Flame retardant polyether urethane

Backus and co-workers [1] investigated the thermal degradation in air of rigid urethane foams by thermogravimetric analysis (TGA), differential thermal analysis (DTA), infrared (IR), and other techniques. Three commercial foams were studied a polyether urethane foam 1, a flame-retardant polyether urethane foam 2, and a chlorinated polyester urethane foam 3 (Table 5.1). 

Figure 5.2 TGA curve of flame-retardant polyether urethane Foam 2 in air heating rate 10 °C/min air flow 0.35 ftVh sample weight 100 mg. Reproduced with permission from J.K. Backus, W.C. Darr, P.G. Gemeinhardt and J.H. Saunders, Journal of Cellular Plastics, 1965, 1, 1, 178. 1965, Sage Publishing [1]...

Temperature (°C) Foam 1 - polyether urethane Foam 2 - flame retardant polyether urethane Foam 3 -chlorinated polyester urethane... 

This method, however, did not result in improved flame retardance because the isocyanurate content was too low. In recent years, however, high-functionality and low-viscosity polyether polyols have become available, and therefore the above method has become less important. Even so, the method was sometimes used to make foams having increased crosslink density to improve dimensional stability or chemical resistance. Therefore, a higher isocyanate index, e.g., 150 to 200, was used to incorporate isocyanurate linkages in rigid urethane foams. 

Poly(urethane) foams based on polyethers have now largely replaced polydiene rubbers in upholstery and flammability is a major disadvantage compared with traditional upholstery. A major problem is that it is not the fire itself that kills people but the toxic fumes that are produced in the smoke and this is exacerbated by certain types of flame retardant. There are no simple solutions to this problem. Foams in their very nature have a large surface area and a developing fire thrives on the accessibility of fuel from the exposed foam (Chapter 3). The most promising solution is to make the textile fabric surrounding the foam non-flammable so that the fire never reaches the foam itself. 

Polyether polyols for rigid urethane foams currently are (August, 1976) priced at 37 - 45 cents/pound while special, flame-retardant polyols command premium prices... 

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